Device for expressing mercury from dental amalgam



Patented Nov. 25, 1952 UNITED STATE TENT OFFICE DEVICE FOR EXPRESSIN G MERCURY FRUM DENTAL AMALGAEI l Claims.

The present invention relates generally to dental tools and equipment, and more particularly to a press for compressing dental amalgam in order to express therefrom free mercury or other liquid constituents.

It has been common practice for many years in the dental profession to use an amalgam of silver, or a silver alloy commonly known as silver amalgam alloy, and mercury for filling cavities in teeth. The amalgam is formed by mixing measured quantities of silver or silver amalgam alloy and mercury, but usually an excess of mercury is provided in order to make sure that all the silver or silver amalgam alloy is amalgamated.

From the standpoint of the physical properties of the finished product, the presence of an excess of mercury is undesirable since it makes the amalgam too soft to be fully serviceable. Furthermore, the presence of free mercury in the amalgam may have detrimental effects upon the final set and hardness of the filling. Consequently, the final step in the preparation of the amalgam has been to express excess mercury, or any other liquid constituent in the amalgam, in order to give a desired degree of dryness to the product for immediate use in packing cavities of teeth and laboratory die models. 7

The expressing of the free mercury has been accomplished by various methods and apparatus. An old but frequently used method has been to Wrap the amalgam in a piece of filtering medium, such as chamois skin or filter cloth and then to apply sufficient pressure with the fingers to express the liquid mercury through the filtering medium. This method has generally resulted in the loss of the excess mercury or its contamina tion even if it is recovered. This method is also objectionable in that there is no way of accurately controlling the pressure applied in order to produce a product having a desired degree of dryness.

In an attempt to improve upon this method, various types of mechanical devices have been provided to act as presses for the amalgam. Most of these have not been entirely satisfactory for one or more reasons. Sometimes the free mercury has been expressed in such a manner that it cannot be collected and used again. Others are hand tools that are not able to apply sufficient pressure to the amalgam to eliminate as much of the liquid content as may be desired. Others are unnecessarily complicated and therefore costly to make and difiicult to clean.

Hence it becomes a general object of my invention to provide a simple form of press within which a charge of amalgam may be compressed to express free mercury therefrom, but without any loss or contamination of the expressed mercury so that it may be used over again.

It is also an object of my invention to provide an amalgam press of this character in which any desired degree of pressure may be applied to the charge in order to control the physical characteristics of the final product.

A further object is to provide a simple form of amalgam press for compressing a quantity of amalgam to express excess mercury therefrom, and for subsequently expelling the resulting body of compressed amalgam.

Another object of my invention is to provide a dental tool of this character which is simple and sturdy in construction in order that it may be economical to manufacture, simple to operate and clean, and able to provide a long period of service.

These and other objects have been accomplished by a device constructed according to my invention by providing a barrel having an internal compression chamber adapted to hold the charge of amalgam. The internal chamber is preferably cylindrical in shape. Two opposed plungers are placed in the chamber, the plungers extending beyond the barrel at opposite ends of the barrel. By effecting relative movement of the plungers toward each other, the charge is compressed. At least one of the plungers has sufficient clearance between it and the inner Wall of the chamber to permit escape of liquid mercury from the compression chamber while at the same time holding the amalgam Within the space between the two plungers. The mercury so expressed is collected in a recess in the barrel or a space between the barrel and cap member attached to one of the plungers, where the free mercury is held securely against loss or contamination. Since any other liquid constituents are also expressed along with the mercury, the term mercury may generally be construed, where applicable, as including any other liquid constituents present. Of course, in a broad sense my invention is independent of any specific materials used in it. After the charge is compressed to the desired degree, one of the plungers is removed from one end of the barrel, and then the other plunger is advanced to expel the plug or compressed charge from the same one end of the barrel.

How the above objects and advantages of my invention, as well as others not specifically referred to herein, are attained will be more readily understood by reference to the following description and to the annexed drawings, in which:

Fig. l is a combined elevation and longitudinal median section illustrating an amalgam press embodying a preferred form of my invention;

Fig. 2 is a view similar to Fig. 1 showing the parts in position for expelling the compressed charge from the compression chamber;

Fig. 3 is a longitudinal median section through a simplified form of my invention; and

Fig. 4 is a longitudinal median section through another form of press constructed according to my invention, embodying features found in both Figs. 1 and 3.

A preferred form of my invention is shown in Figs. 1 and 2. The amalgam press of this embodiment includes barrel l6 of which a section is preferably provided with external threads H extending inwardly from one end of the barrel. The remainder of the barrel may be provided at l2 with an external knurled surface to permit a good grip to be obtained on the barrel, or it may be finished with two or more fiat sides so that a wrench or like tool may be applied to the barrel. An example of this construction is the conventional hexagonal shape used for nuts and bolts.

Within barrel Ell is located compression chamber id which is preferably cylindrical in shape. At one end, compression chamber ifopens directly to the exterior of the barrel. The other endof compression chamber M opens to the out side of barrel ii) through an extension bore it which is of smaller diameter than chamber is, thus producing an annular shoulder inside the barrel at this end of the compression chamber.

Inside the compression chamber are two opposed plungers, 23 and 2 l. Plunger 28 has a head portion Zea which is substantially the full diameter of chamber M, its diameter being preferably only about .001-.OO2 inch less than the internal diameter of the compression chamber in order to produce a snug working fit between the head portion Zta of the plunger and the compression chamber wall. This fit is sufficiently tight to prevent any appreciable amount of mercury or amalgam from working past the plunger, and yet permits the plunger to be turned relative to the barrel and to move longitudinally therein. Plunger 2i has a shank portion 2%!) of smaller diameter than the head projecting outwardly beyond the end of the barrel, through the extension bore iii, a portion of the shank being threaded as indicated at ildc in order to engage corresponding threads at a in the bore iii of barrel 19. The outer end of shank 23b of plunger Ell is provided with knob 22 wiich may be fastened upon the plunger in any suitable manner to cause movement of the plunger by turning the knob. It is preferred that the connection between knob 22 and the plunger 28 be of such type that the knob can easily be i sad and removed from the plunger in order to permit the plunger to be removed from the barrel through the compression chamber for cleaning or servicing. As an example, I have shown the shank b threadedly secured within a threaded bore 22a in knob 22 and having a reduced end portion 29d adapted to seat firmly against the inner end of said bore. The exterior of knob 22 is here shown as being finished with a knurled external surface 22b; but it may also be finished with two or more flat faces adapted to take a wrench.

Plunger 2| enters the compression chamber from the end opposite the plunger 20, that is, from the end which opens directly to the exterior of the barrel. Plunger 21 is cylindrical to conform to the configuration of the compression chamber, but is of slightly smaller diameter in order to provide a clearance between the plunger and the wall of the chamber through which mercury may pass to escape from the compression chamber. At the same time, this clearance is not sufficiently large to permit the amalgam, or at least any appreciable quantity of the amalgam, to escape along with the liquid mercury. I have found by experience that a clearance in the neighborhood of Bill-.002 inch around plunge 2| is sufficient to hold amalgam in the compression chamber yet allow the escape of the liquid mercury. In other words, the diameter of plunger 2i is in the neighborhood of 1102-.004 inch less than the internal diameter of the compression chamber. However, I do not wish my invention to be necessarily limited to these particular clearances since a clearance around plunger 2| slightly in excess of .002 inch may be used quite successfully, depending upon various factors. Also, both plungers may have the larger clearance, permitting mercury to escape past both plungers.

Plunger 21 is connected by means of its shank 2m to cap 25 which may be provided with a knurled external surface 26a or otherwise finished externally in a manner comparable to knob or barrel Hi, to facilitate rotation. Cap 24 is provided with a central bore 25 having internal threads at 25c which engage threads H on the barrel so that relative rotation of the cap and barrel causes plunger 2| to move axially within chamber I l with respect to plunger 20. The axial length of bore 25 is such that the outer end of barrel [9 is always spaced at least a short distance from the inner ends of said bore to leave an annular recess or space 26 around the base of plunger 2!. This ecess 26 receives and holds the mercury which escapes from compression chamber it around plunger 2!.

Before placing a charge of amalgam in chamber i i, cap 24 and plunger 2! are removed and it is preferable, although not necessary, to back off plunger 26 until the head of the plunger comes into contact with annular shoulder 16. The charge is then loaded into compression chamber M, as indicated for example in dotted lines at A, and cap 24 is screwed onto the barrel, causing plunger 2| to advance within the compression chamber toward the other plunger 2.). Relative rotational movement of the barrel and the cap causes relative movement of the two plungers, bringing them toward each other to compress the charge in the compression chamber. The charge may be compressed by manual rotation of cap 24 and plunger 2!, or knob 22 and plunger 20, relative to barrel ill, to cause inward movement of only the plunger that is rotated relative to the barrel. In general, however, I prefer to effect such compression by grasping cap 25 in one hand and knob 22 in th other hand and thereby rotating the two plungers relative to each other and to the barrel, so that both plungers are moved inwardly within the compression chamber I4; For this purpose, the coacting threads on all of these members are preferably all of the same hand. Free mercury is expressed from the charge and escapes from the compression chamber around plunger 2 i, by virtue of the clearance between the plunger and the inner wall of the compression chamber. around plunger 2| is collected in recess 26. After the desired degree of compression has been given This mercury escaping to the charge in the compression chamber, cap 2 3 is rotated in the reverse direction, causing plunger 2! to recede from plunger 25. Mercury in the recess remains there until the cap is inverted and shaken, allowing the mercury to drop out. As a final step in the operation, plunger is advanced towards the now open end of the compression chamber by rotating knob 22. This motion of the plunger moves the plug A of compressed amalgam toward the open end of the compression chamber, as shown in Fig, 2, the range of plunger movement being sufiicient to expel the plug from the press.

It will be readily apparent from Fig. 2 that by continuing the movement of plunger 20 toward the open end of the compression chamber through which plunger 2! has previously been removed, and by removing knob 22 from plunger shank Zilb, that plunger 20 may also be withdrawn from the barrel and the compression chamber through this same end of the compression chamber.

Fig. 3 illustrates a simplified form of my invention in which barrel 3%] is not provided with a cap or other member threadedly engaging the barrel. The two plungers SI and 32 enter the barrel from opposite ends. The working ends of the plungers are located in compression chamber which, as before is cylindrical and extends entirely through the barrel. Plungers 3i and 52-2 are preferably smooth to either slide or rotate with respect to the barrel. The clearances between plungers 3i and 32 and the walls of the compression chamber are the same as described above for plungers 2i and 253 respectively. Barrel 33 is counterbcred concentrically of compression chamber in order to provide an annularly shaped chamber or recess 35, preferably undercut as shown at 35a, in which mercury is collected after it escapes from the compression chamber around plunger 35. This mercury collecting chamber operates in the same manner as the chamber 2%, previously described.

In order to charge the compression chamber in this form of amalgam press, either one of plungers iii or 32 is inserted in the compression chamber, and then the amalgam is loaded into the chamber through the open end. After the charge is in place, the other plunger is inserted in the remaining end of the chamber to close it, the parts then occupying a position somewhat as shown in Fig. 3. In this form of the invention, endwise compressing forces are applied directly to the two plungers 3! and 32 by some type of external means. As typical of such means, I have shown at 31 and 38 two opposed jaws of an ordinary type of bench vise. Force may be applied to the jaws by a conventional type of lead screw, fluid pressure operated cylinder, or other means conventional and well-known with Vises which constitute no part of the present invention.

it is also possible to apply endwise thrust to plungers 3! and 32, which produces relative movement of the plungers toward each other, by hand operated devices such as pliers, tongs, or rackand-pinion devices which enable the operator to gain a mechanical advantage. Alternatively, the amalgam press may be turned with the plungers vertical and one of them, preferably the plunger 32, rested upon an anvil. The upper one then may be struck with a hammer to produce the compressive relative movement of the two plungers. Obviously, any of the embodiments disclosed can be used in a vertical or other, as well as horizontal, position.

Since compression chamber 34 is of uniform minimum diameter throughout its entire length and in effect opens to the exterior of barrel 3d at both ends, both plungers may be withdrawn from the compression chamber. After the charge is compressed plunger ti preferably is first withdrawn from the compression chamber and then the remaining plunger 32 pushed into and through the compression chamber to expel the compressed charge at the same end as that at which the first plunger 3! was removed.

Fig. 4 illustrates another variational form of my invention in which barrel ill and cap 24 are constructed as described in connection with the embodiment disclosed in Fig. 1. As compared with the embodiment in Fig. 1, the differences lie in modification of plungers id and d! and in omission of the threaded engagement between shank 68a of plunger tit and bore l 5 in the barrel.

Since the shank of plunger id is free to slide within bore i5, it may be driven forward into the compression chamber as a result of pressure applied to the outer end of plunger shank diia which projects beyond barrel it, in a manner similar to that described in connection with plunger 32 of Fig. 3. Plunger ill has been modified from the shape shown for plunger 2i by adding slightly to its length so that the opposed faces of the two plungers may be brought into contact with each other in the compression chamber. This adapts the press to very small quantities of amalgam since the approach of the two plungers toward each other is not hindered by engagement of any other parts of the press. When the two plungers are advanced toward each other until they have come into mutual contact, the parts occupy the position shown in full lines in Fig. l. Normally plungers ii! and 4%! are separated by a substantial amount determined by the size of the charge in the compression chamber and at the beginning of the compression stroke cap 25 occupies some such position as indicated by the dot-dash lines of Fig. 4.

The operation of the form of my invention disclosed in i should be obvious from the foregoing description. Relative movement of the two plungers in the compression chamber to apply pressure to the charge therein is preferably accomplished by relative rotation of the cap and barrel, as these two members are interconnected by engagement of threads ii and 25. After the charge is compressed, cap 25 is unscrewed and plunger d! removed from one end of the compression chamber. The compressed charged is subsequently removed through the same end of the chamber by force applied endwise to the outer end of the shank of plunger til, which force moves plunger 49 toward said one end of the chamber.

In the forms of press shown in Figs. 1 and 4, the barrel and cap, and the knob 22 if any, are of relatively large diameter and, as mentioned above, knurled on the outside. This permits relative rotation of the parts to be accomplished manually, and the pressure thus exerted on the amalgam is sufiicient for most purposes in regular dental use. If greater pressures are needed in the preparation of amalgam bodies for certain purposes, then the exterior surfaces of these parts may be finished to accommodate Wrenches or other means for applying greater leverage for turning the parts of the press. In the form of Fig. 4, additional compressive forces may be applied by endwise thrust on plunger 40, as from aelasee hammer blows, after the barrel and cap have been-tightened as far as possible manually.

From the foregoing description it will be ap parent that various changes in the construction and arrangement of parts of my improved press may be made without departing from the spirit and scope of my invention. Consequently, I wish it understood that the foregoing description is considered as illustrative or rather than restrictive upon the appended claims.

I claim:

1. In an amalgam press, the combination comp 'i'sing: a barrel having an internal oylindrical compression chamber adapted to hold a charge of amalgam; two opposed plunger-s in the chamber movab e relatively toward each other to compress the charge, at least one of the plungers having sufficient clearance around it to permit escape of liquid mercury from the compression chamber through said clearance but to hold amalgam in the chamber; and screw thread means interconnecting one of the plungers and the barrel to produce relative movement of the two plungers by relative rotation of the th *eaded plunger and barrel.

2. In an amalgam press, the combination comprising: a barrel having an internal cylindrical compression chamber adapted to hold a charge of amalgam; two opposed plungers in the chamber movable relatively toward each other to compress the charge, at least one of the plungers having sufiicient clearance around it to permit escape of liquid mercury from the compression chamber through said clearance but to hold amalgam in the chamber; and screw thread means connecting each of the plungers inclividually to the barrel to produce relati e movement of the plungers toward each other by relative rotation.

3. In an amalgam press, the combination comprisin a barrel having an internal compression chamber adapted to hold a charge of amalgam; a first plunger movable within the chamber and projecting beyond the barrel at one end, the plunger having sufiicient clearance around it to permit liquid mercury to escape from the compression chamber through said clearance but to hold amalgam in the chamber; and a second plunger movable within the chamber, relative movement of the plungers toward each other compressing the charge of amalgam, the first plunger being removable from the chamber at one end and the second plunger having a sufficient range of movement to expel the compressed charge at said one end, the second plunger extending beyond the barrel at the end opposite to the first plunger to permit application to the second plunger of forces to move the plunger; said second plunger threadedly engaging the barrel and being movable relative to the barrel by application of rotative forces.

4. In an amalgam press, the combination cornprising: a barrel having an externally threaded section and internal compression chamber adapted to hold a charge of amalgam; a first plunger movable Within the chamber and projecting beyond the barrel at one end, the plunger having sufiicient clearance around it to permit liquid mercury to escape from the compression chamber through said clearance but to hold amalgam in the chamber; a second plunger movable within the chamber, relative movement of the plungers toward each other compressing the charge of amalgam, the first plunger being removable from the chamber at one end and the second plunger having a sufficient range of movement to expel the compressed charge at said one end, the second plunger extending beyond the barrel at the end opposite to the first plunger to permit application to the second plunger of forces to move the plunger; and a cap member internally threaded to engage the threaded section on the barrel and connected to the first plunger to move the first plunger therewith relative to the barrel, said cap and barrel cooperating to form an annular space around the first plunger for receiving and retaining mercury escaping from the compression chamber through said clearance around said first plunger.

HARRY H. LYON.

REFERENCES CITED The following references are of record in'the file of this patent:

UNITED STATES PATENTS 

